Welcome to our KN forum. I'm sure you will find a warm welcome here from all of us and plenty of help should you need it. I just checked in and saw your first post. I have a KN6000 and have installed the SY-EW65NX card, so perhaps I can shed some light on your question.
The SY-EW65NX card is a wave expansion board upgrade kit. In essence it converts your KN6000 to a KN6500. There are 60 additional (new) sounds, six of which are piano sounds. The piano sounds added are: Concert Grand; Mono Grand; Upright Piano; Pop Grand; Mellow Grand; and, Baby Grand. I use the concert grand voice almost exclusively. I like its richness and fullness. I use the other piano voices so little that I don't believe I can make a meaningful comparison of sounds for you. The SY-EW65NX upgrade card has 20 piano sounds and round about 1100+ sounds in total.
The EW-01, EW-02, EW03, and EW-04 cards are sound expansion cards and have many useful voices. Some are excellent and others middle of the road. I have the 01, 02, and 03 cards. The 03 card does not have any acoustic piano voices but does provide 18 electric piano voices. There are no piano voices included among the sounds on the 01 and 02 cards. I do not have the 04 card yet but think I will purchase it soon.
Since I have the 65 card installed and the KN6000 has only two expansion slots, I can only use one card at a time. The KN7000 has four expansion slots so it will accomodate all four cards. That is a significant advantage.
I am certain that if you contact Technote International by e-mail, someone there would be happy to give you all the details concerning the content of the cards I have been discussing. Their website address is as follows: http://www.technote.com/home.asp
If I can be of further help to you just ask. I will try my best to answer your questions.